Cylindrical-shaped workpiece evaluation method and evaluation apparatus

Abstract

To provide an evaluation method and an evaluation apparatus for a cylindrical-shaped workpiece designated by a shape developed on a two-dimensional plane. A single two-dimensional reference shape data is substantially designated from a hard disk which includes a plurality of two-dimensional reference shape data based on a two-dimensional shape displayed on a two-dimensional plane where a curved surface of a reference cylindrical-shaped workpiece is developed. A reference cylindrical-shaped workpiece having a curved surface with a two-dimensional shape corresponding to the read two-dimensional reference shape data is converted by a converter into a surface shape of the reference cylindrical-shaped workpiece. In addition, a surface shape of an evaluation object cylindrical-shaped workpiece is measured, and a distance between a measurement point in the measurement and a point in the surface shape of the reference cylindrical-shaped workpiece corresponding to the measurement point is obtained by a calculator. The distance obtained by the calculator is overlay-displayed as an error on the two-dimensional shape corresponding to the two-dimensional reference shape data read from the hard disk, under the control of a display controller. The evaluation object cylindrical-shaped workpiece is evaluated based on the two-dimensional display where the error is overlay-displayed.

What is claimed is:  
     
       1. A cylindrical-shaped workpiece evaluation method comprising the steps of: 
       reading two-dimensional reference shape data, based on a two-dimensional shape designated by a designation means, from a storage means holding a plurality of two-dimensional reference shape data based on a two-dimensional shape displayed on a two-dimensional plane, where a curved surface of a reference cylindrical-shaped workpiece is developed;  
       converting the reference cylindrical-shaped workpiece having a two-dimensional-shaped curved surface corresponding to the two-dimensional reference shape data read at said reading step into a surface shape of said reference cylindrical-shaped workpiece;  
       measuring a surface shape of an evaluation object cylindrical-shaped workpiece and obtaining a distance between a measurement point in said measurement and a point in the surface shape of the reference cylindrical-shaped workpiece converted at said converting step, corresponding to said measurement point; and  
       overlay-displaying the distance obtained at said measuring step as an error on the two-dimensional shape corresponding to the two-dimensional reference shape data read at said reading step,  
       wherein the evaluation object cylindrical-shaped workpiece is evaluated based on the two-dimensional display where the error is overlay-displayed at said overlay-displaying step.  
     
     
       2. The cylindrical-shaped workpiece evaluation method according to  claim 1 , wherein said surface shape of said reference cylindrical-shaped workpiece corresponds to coordinate position data in a three-dimensional orthogonal coordinate system, said step of measuring further comprising the step of measuring a surface shape of said evaluation object cylindrical-shaped workpiece as three-dimensional orthogonal coordinate system data with a three dimensional measuring machine. 
     
     
       3. The cylindrical-shaped workpiece evaluation method according to  claim 2 , said step of obtaining further comprising the steps of: 
       comparing three-dimensional data of mutually-corresponding points in the measurement data based on the surface shape of the evaluation object cylindrical-shaped workpiece with the measurement data based on the surface shape of the reference cylindrical-shaped workpiece; and  
       calculating a distance between the corresponding points.  
     
     
       4. A cylindrical-shaped workpiece evaluation apparatus comprising: 
       storage means for storing a plurality of two-dimensional reference shape data based on a two-dimensional shape displayed on a two-dimensional plane where a curved surface of a reference cylindrical-shaped workpiece is developed;  
       designation means for designating one two-dimensional reference shape data read from said storage means based on the two-dimensional shape;  
       conversion means for converting the reference cylindrical-shaped workpiece having a curved surface having a two-dimensional shape corresponding to the two-dimensional shape data read from said storage means into a surface shape of said reference cylindrical-shaped workpiece;  
       calculation means for measuring a surface shape of an evaluation object cylindrical-shaped workpiece and obtaining a distance between a measurement point in said measurement and a point in the surface shape of the reference cylindrical-shaped workpiece converted at said second step, corresponding to said measurement point;  
       display control means for overlay-displaying the distance obtained by said calculation means as an error on the two-dimensional shape corresponding to the two-dimensional reference shape data read from said storage means,  
       wherein the evaluation object cylindrical-shaped workpiece is evaluated based on the two-dimensional display where the error is overlay-displayed.  
     
     
       5. The cylindrical-shaped workpiece evaluation apparatus according to  claim 4 , wherein said surface shape of said reference cylindrical-shaped workpiece corresponds to coordinate position data in a three-dimensional orthogonal coordinate system, and said calculation means measures a surface shape of said evaluation object cylindrical-shaped workpiece as three-dimensional orthogonal coordinate system data with a three dimensional measuring machine. 
     
     
       6. The cylindrical-shaped workpiece evaluation apparatus according to  claim 3 , wherein said calculation means compares three-dimensional data of mutually-corresponding points in the measurement data based on the surface shape of the evaluation object cylindrical-shaped workpiece with the measurement data based on the surface shape of the reference cylindrical-shaped workpiece and calculates a distance between the corresponding points. 
     
     
       7. A cylindrical-shaped workpiece evaluation method comprising the steps of: 
       designating a two-dimensional shape representing a curved surface of a reference cylindrical-shaped workpiece;  
       obtaining a surface function of a cylindrical shape in the reference cylindrical-shaped workpiece;  
       converting the surface function of the cylindrical shape into a three-dimensional surface shape of said reference cylindrical-shaped workpiece;  
       measuring a three-dimensional surface shape of an evaluation object cylindrical-shaped workpiece;  
       obtaining a distance between a measurement point in said measurement and a point in the surface shape of the reference cylindrical-shaped workpiece, corresponding to said measurement point; and  
       calculating an error by comparison between the three-dimensional surface shape of reference cylindrical-shaped workpiece and the three-dimensional measurement data;  
       converting surface function of cylindrical shape in reference cylindrical-shaped workpiece into a two-dimensional function; and  
       generating two-dimensional data; and  
       displaying calculated error based on two-dimensional data.  
     
     
       8. The cylindrical-shaped workpiece evaluation method according to  claim 7 , wherein said surface shape of said reference cylindrical-shaped workpiece corresponds to coordinate position data in a three-dimensional orthogonal coordinate system, said step of measuring further comprising the step of measuring a surface shape of said evaluation object cylindrical-shaped workpiece as three-dimensional orthogonal coordinate system data with a three dimensional measuring machine. 
     
     
       9. The cylindrical-shaped workpiece evaluation method according to  claim 8 , said step of obtaining further comprising the steps of: 
       comparing three-dimensional data of mutually-corresponding points in the measurement data based on the surface shape of the evaluation object cylindrical-shaped workpiece with the measurement data based on the surface shape of the reference cylindrical-shaped workpiece; and  
       calculating a distance between the corresponding points.